Do I have to inform the FCC if I decide to sign the station off from (for example) 3AM to 7AM? What about the EAS?

If you are not in a time share situation, you are not required to contact the FCC if you not broadcast for a short period. Notification is only required if the station is going "silent" for a longer period of time. LPFM stations must maintain a minimum schedule of 5 hours per day, 6 days per week (LPFM stations licensed to schools are not required to broadcast during vacation periods). During the time that you are not on the air, you have no EAS obligations.